Synthesize retinoids for in vitro studies. The approach will involve the synthesis of several different retinoids, the choice of which will be dictated by the needs and interest of the NCI Carcinogenesis Program. In general, the contractor will: synthesize a variety of active metabolites of retinoic acid; prepare some selected retinoic acid analogs by isosteric substitution; synthesize the amino acid and glyceride molecular modifications of retinoic acid; submit all retinoids and synthetic retinoic acids to NCI for biological evaluation; and supply project officer with data documentating the chemical purity of each compound and a small sample on which NCI personnel can determine the purity.